CN102646772A - A light-emitting diode with a back plating structure - Google Patents

Abstract

The invention discloses a light-emitting diode (LED) with back plating structure, which comprises a p-electrode, an n-electrode and a substrate with a non-emergent surface and an emergent surface, wherein an n-type GaN layer, a quantum well, a p-type GaN layer, an indium tin oxide layer and a passivation layer are sequentially arranged on the emergent surface of the substrate; the p-electrode is positioned on the upper surface of the indium tin oxide layer; the n-electrode is positioned on the upper surface of the n-type GaN layer; a Bragg reflection layer is arranged on the non-emergent surface of the substrate; the Bragg reflection layer is formed by alternately arranging aluminum oxide layers and titanium dioxide layers, and the aluminum oxide layer and the adjacent titanium dioxide layer are attached to each other; and the refractivity of the aluminum oxide layer is less than that of the titanium dioxide layer. The LED in the structure can enhance the light extraction efficiency of the LED.

Description

A kind of light-emitting diode with back of the body plating structure

Technical field

The invention belongs to the semiconductor lighting device, specifically, relate to a kind of light-emitting diode with back of the body plating structure.

Background technology

In recent years; Basic LED (the light-emitting diode of gallium nitride (chemical formula is GaN); English full name " Light Emitting Diode " is called for short " LED ") development is swift and violent. and with LED is the semiconductor illuminating light source of core, will replace incandescent lamp, fluorescent lamp future and becomes lighting source of new generation.Gallium nitride based LED construction is as shown in Figure 1, comprises p electrode, SQW, passivation layer, indium tin oxide layer, p type GaN layer, n electrode, n type GaN layer and substrate.Therefore yet still there are problems such as luminous efficiency is low, cost is high, poor reliability at present in LED, and the luminous efficiency of commercial white light LEDs is also lower, has limited its march toward speed of illumination and other application.

LED is as a kind of light source, and an important indicator weighing it is exactly photoelectric conversion efficiency or luminous efficiency.Two basics point of departure that improve the LED luminous efficiency improve its internal quantum efficiency and external quantum efficiency exactly.The external quantum efficiency η of LED_Ex=η_InC_Ex, in the formula, η_InIt is internal quantum efficiency; C_ExIt is light extraction efficiency.Because the light extraction efficiency of GaN base LED is very low, and internal quantum efficiency can reach very high level, becomes the key that improves LED external quantum efficiency that is luminous efficiency so improve the light extraction efficiency of LED.For traditional Sapphire Substrate GaN base LED; It is many-sided causing the low-down reason of light extraction efficiency; Comprise lattice defect to the absorption of light, substrate to absorption, inside (repetition) of light absorb, the light of the stopping of electrode, particularly LED emission is in the outgoing process; Owing to the reasons such as light loss that cause with the total reflection between the glue in chip and encapsulation, so that only have 4% the light can be from the surperficial outgoing of LED, most light then be limited in LED inside; Finally become thermal losses, thereby cause extremely low light extraction efficiency.Therefore, the light extraction efficiency that how to improve LED is one of research topic that needs to be resolved hurrily most in the field of semiconductor illumination.

Summary of the invention

Technical problem:Technical problem to be solved by this invention is: a kind of light-emitting diode with back of the body plating structure is provided, improves the light extraction efficiency of LED.

Technical scheme:For solving the problems of the technologies described above, the technical scheme that the present invention adopts is:

A kind of light-emitting diode with back of the body plating structure; Comprise p electrode, n electrode and have the substrate of non-exiting surface and exiting surface; On the exiting surface of substrate, be sequentially with n type GaN layer, SQW, p type GaN layer and indium tin oxide layer and passivation layer; The p electrode is positioned at the upper surface of indium tin oxide layer, and the n electrode is positioned at the upper surface of n type GaN layer, and the non-exiting surface of described substrate is provided with Bragg reflecting layer; This Bragg reflecting layer is alternately rearranged by alundum (Al layer and titanium dioxide layer, and pastes each other between adjacent alundum (Al layer and the titanium dioxide layer; The refractive index of alundum (Al layer is less than the refractive index of titanium dioxide layer.

Described light-emitting diode with back of the body plating structure also comprises metallic reflector, and this metallic reflector is positioned at the outer surface of Bragg reflecting layer.

Beneficial effect:Compared with prior art, the present invention has following beneficial effect:

1.LED light extraction efficiency high.In the prior art, only have 4% the light can be from LED surface outgoing, most light then be limited in LED inside, finally becomes thermal losses.And in the technical scheme of the present invention; The non-exiting surface of light-emitting diode substrate is provided with Bragg reflecting layer; Can the light of directive chip bottom be utilized Bragg reflection principle reflected back upper surface; The reflectivity of Bragg reflecting layer can reach more than 90%, thereby improves the LED external quantum efficiency, and then improves the light extraction efficiency height of LED.

2. have good thermal conductivity, help the heat radiation of led chip.In the technical scheme of the present invention, one metallic reflector can be set at the outer surface of Bragg reflecting layer.Metallic reflector can further improve reflectivity.In addition, metallic reflector has good thermal conductivity, helps the heat radiation of led chip.Especially for great power LED, metallic reflector has important value to the thermal diffusivity that improves LED.

Description of drawings

Fig. 1 is the gallium nitride based LED construction sketch map of Sapphire Substrate in the prior art.

Fig. 2 is a structural representation of the present invention.

Fig. 3 is a kind of improvement structural representation of the present invention.

Fig. 4 is the structural representation of the Bragg reflecting layer of Fig. 2, and two arrow lines that are positioned at the top are represented incident ray and reflection ray.

Fig. 5 is the Bragg reflecting layer of Fig. 3 and the structural representation of metal level, and two arrow lines that are positioned at the top are represented incident ray and reflection ray.

Have among the figure:p electrode 1,SQW 2,passivation layer 3, ITO4, ptype GaN layer 5,n electrode 6, ntype GaN layer 7,substrate 8, Bragg reflectinglayer 9, alundum (Al layer 91,titanium dioxide layer 92,metallic reflector 10.

Embodiment

Below in conjunction with accompanying drawing, technical scheme of the present invention is elaborated.

As shown in Figure 2; A kind of light-emitting diode of the present invention with back of the body plating structure; Comprisep electrode 1,n electrode 6 and have thesubstrate 8 of non-exiting surface and exiting surface; On the exiting surface ofsubstrate 8, be sequentially with ntype GaN layer 7,SQW 2, p type GaN layer (GaN is the chemical formula of gallium nitride) 5 and indium tin oxide layer 4 andpassivation layer 3,p electrode 1 is positioned at the upper surface of indium tin oxide layer 4, andn electrode 6 is positioned at the upper surface of n type GaN layer 7.The non-exiting surface ofsubstrate 8 is provided with Bragg reflecting layer 9.Substrate 8 adopts sapphire, GaAs, carborundum or silicon materials to process.Bragg reflectinglayer 9 is alternately rearranged by alundum (Al layer 91 andtitanium dioxide layer 92, and pastes each other between adjacent alundum (Al layer 91 and the titanium dioxide layer 92.The refractive index of alundum (Al layer 91 is less than the refractive index of titanium dioxide layer 92.That is to say; As shown in Figure 4, first alundum (Al layer 91 is covered on the non-exiting surface ofsubstrate 8, firsttitanium dioxide layer 92 is covered on the outer surface of first alundum (Al layer 91 again; Then second alundum (Al layer 91 is covered on the outer surface of firsttitanium dioxide layer 92; Then secondtitanium dioxide layer 92 is covered on the outer surface of second alundum (Al layer 91 ..., circulate with this.Certainly; It also can be the non-exiting surface that earlier firsttitanium dioxide layer 92 is covered onsubstrate 8; Again first alundum (Al layer 91 is covered on the outer surface of firsttitanium dioxide layer 92, then secondtitanium dioxide layer 92 is covered on the outer surface of first alundum (Al layer 91, then second alundum (Al layer 91 is covered on secondtitanium dioxide layer 92 outer surface;, circulate with this.Alundum (Al layer 91 in the Bragg reflectinglayer 9 is identical with the number of plies oftitanium dioxide layer 92, and alundum (Al layer 91 respectively is 1 layer-20 layers with titanium dioxide layer 92.That is to say that alundum (Al layer 91 is alternately arranged 1 time-20 times withtitanium dioxide layer 92, for example can be 1 time, 5 times, 8 times, 10 times, 15 times, 18 times or 20 times.The optical thickness of the optical thickness of alundum (Al layer 91 andtitanium dioxide layer 92 is respectively 1/4 of reverberation wavelength.Also promptly, the optical thickness of alundum (Al layer 91 is 1/4 refractive indexes divided by alundum (Al layer 91 of lambda1-wavelength, and the optical thickness oftitanium dioxide layer 92 is 1/4 refractive indexes divided bytitanium dioxide layer 92 of lambda1-wavelength.

Further, like Fig. 3 and shown in Figure 5, described light-emitting diode with back of the body plating structure also comprisesmetallic reflector 10, and thismetallic reflector 10 is positioned at the outer surface of Bragg reflecting layer 9.Outer surface at Bragg reflectinglayer 9 is provided with a metallic reflector 10.Bragg reflectinglayer 9 can both improve reflectivity withmetallic reflector 10, and the thermal conductivity ofmetallic reflector 10 is good, so have good thermal conductivity.The combination of Bragg reflectinglayer 9 andmetallic reflector 10 has high reflectance and good thermal conductivity to the corresponding wave band of LED emergent light, and the heat dissipation characteristics that improves great power LED is had important value.The thickness of describedmetallic reflector 10 is between 50 nm-300 nm.Thismetallic reflector 10 is made of aluminum.Certainly, can also select other metal materials, for example silver.But when being to use silver-colored material, then needing on silver, plate the sulfuration that layer of metal nickel prevents silver again, or take other anti-sulfuration measure.

The present invention increases on the non-exiting surface of thesubstrate 8 of existing light-emitting diode Bragg reflectinglayer 9 is set, and Bragg reflectinglayer 9 is formed by alundum (Al layer 91 and 92 two kinds of material alternate combinations of titanium dioxide layer.Bragg reflectinglayer 9 can be with the light that is originally absorbed by chip bottom reflected back LED again, thereby can significantly improve the light extraction efficiency of LED.

Only two surperficial outgoing up and down that the active area of LED sends, and packaged LED is that " unidirectional " is luminous, therefore is necessary light reflection or directly outgoing with the directive chip bottom.In the light-emitting diode of the present invention, after incident light was injected, Bragg reflectinglayer 9 can utilize the light of directive chip bottom Bragg reflection principle reflected back upper surface, thereby improved the LED external quantum efficiency.The optical thickness of the alundum (Al layer 91 in the Bragg reflectinglayer 9 and the optical thickness oftitanium dioxide layer 92 are respectively 1/4 of reverberation wavelength.Bragg reflectinglayer 9 is a kind of quarter-wave sandwich constructions, is equivalent to simple 1-D photon crystal.Because the electromagnetic wave that frequency drops in the energy gap scope can't penetrate, the reflectivity of Bragg mirror can reach more than 90%.The energy gap position can be adjusted through the refractive index or the thickness that change alundum (Al layer 91 ortitanium dioxide layer 92.

Gallium nitride based LED construction with Sapphire Substrate is an example, specifies the high advantage of light extraction efficiency that light-emitting diode of the present invention has.

As shown in Figure 2, light-emitting diode comprisesp electrode 1,SQW 2,passivation layer 3, indium tin oxide layer 4, ptype GaN layer 5,n electrode 6, ntype GaN layer 7,substrate 8, Bragg reflectinglayer 9 and metallic reflector 10.Growing n-type GaN layer 7 on the exiting surface ofsubstrate 8; The upper surface grownquantum trap 2 and then electrode 6 of ntype GaN layer 7; The upper surface growing p-type GaN layer 5 ofSQW 2, the upper surface growth indium tin oxide layer 4 of ptype GaN layer 5, the upper surfacegrowth p electrode 1 and thepassivation layer 3 of indium tin oxide layer 4.GrowthBragg reflecting layer 9 on the non-exiting surface ofsubstrate 8, the outer surface growingmetal reflector 10 of Bragg reflecting layer 9.Bragg reflectinglayer 9 is alternately to be arranged withtitanium dioxide layer 92 by alundum (Al layer 91 to form.

Employing is the blue-light LED chip of 450 nm with peak wavelength, and the optical thickness oftitanium dioxide layer 92 is 44 nm, and the optical thickness of alundum (Al layer 91 is 66 nm, andtitanium dioxide layer 92 is provided with 6 layers respectively with alundum (Al layer 91.During incident light vertical incidence LED, can obtain the reflectivity more than 95%.

LED as shown in Figure 3, its structure is identical with LED structure shown in Figure 2, and different is to be provided with layer ofmetal reflector 10 at Bragg reflectinglayer 9 outer surfaces.

Employing is the blue-light LED chip of 450 nm with peak wavelength, and the optical thickness oftitanium dioxide layer 92 is 44 nm, and the optical thickness of alundum (Al layer 91 is 66 nm, andtitanium dioxide layer 92 is provided with 3 layers respectively with alundum (Al layer 91.Metallic reflector 10 adopts aluminum to process, and the thickness ofmetallic reflector 10 is 100 nm.During incident light vertical incidence LED, can obtain the reflectivity more than 98%.

Above-described specific embodiment has carried out further detailed explanation to the object of the invention, technical scheme and beneficial effect.But should be emphasized that the above embodiment is merely preferred embodiments of the present invention, is not to be used to limit protection scope of the present invention.All within spirit of the present invention and principle, any modification that the back of the body of the present invention plating structure is made, replacement, improvement etc. all should be included in protection scope of the present invention.

Claims (7)

1. one kind has the light-emitting diode that the back of the body plates structure; Comprise p electrode (1), n electrode (6) and have the substrate (8) of non-exiting surface and exiting surface; On the exiting surface of substrate (8), be sequentially with n type GaN layer (7), SQW (2), p type GaN layer (5) and indium tin oxide layer (4) and passivation layer (3); P electrode (1) is positioned at the upper surface of indium tin oxide layer (4); N electrode (6) is positioned at the upper surface of n type GaN layer (7), it is characterized in that, the non-exiting surface of described substrate (8) is provided with Bragg reflecting layer (9); This Bragg reflecting layer (9) is alternately rearranged by alundum (Al layer (91) and titanium dioxide layer (92), and pastes each other between adjacent alundum (Al (91) layer and the titanium dioxide layer (92); The refractive index of alundum (Al layer (91) is less than the refractive index of titanium dioxide layer (92).

2. according to the described light-emitting diode of claim 1, it is characterized in that also comprise metallic reflector (10), this metallic reflector (10) is positioned at the outer surface of Bragg reflecting layer (9) with back of the body plating structure.

3. according to the described light-emitting diode of claim 2, it is characterized in that the thickness of described metallic reflector (10) is between 50 nm-300 nm with back of the body plating structure.

4. according to the described light-emitting diode of claim 3, it is characterized in that described metallic reflector (10) is made of aluminum with back of the body plating structure.

5. according to any one described light-emitting diode in the claim 1 to 4, it is characterized in that the optical thickness of the optical thickness of described alundum (Al layer (91) and titanium dioxide layer (92) is respectively 1/4 of reverberation wavelength with back of the body plating structure.

6. according to the described light-emitting diode of claim 5 with back of the body plating structure; It is characterized in that; Alundum (Al layer (91) in the described Bragg reflecting layer (9) is identical with the number of plies of titanium dioxide layer (92), and alundum (Al layer (91) and titanium dioxide layer (92) respectively are 1 layer-20 layers.

7. according to the described light-emitting diode of claim 1, it is characterized in that described substrate (8) adopts sapphire, GaAs, carborundum or silicon materials to process with back of the body plating structure.

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